Heretofore, an elongated housing upon a suitable support mounted parallel spaced tracks upon which was reciprocally supported a carriage adapted to mount a gripping tool for transferring workpieces into and out of a machine tool as for example, a press or stamping die. Opposed rack gears were mounted upon the housing and the carriage. A power reciprocated pinion carrier included a plurality of pairs of laterally spaced pinions in mesh with the respective rack gears so that reciprocation of the pinion carrier effected corresponding reciprocal movements of the carriage. The problem existed of supporting and guidably mounting the pinion carrier so that its reciprocal movements were constrained to a single horizontal plane and to a single vertical plane.